As a programmer, this argument really bothers me, especially when it's actually used by gaming developers. Almost invariably you'll have some discussion like 'why is X overpowered' or 'Z should be changed' and some people will make this argument, but today I actually saw a Blizzard developer answer to why bosses in Alterac Valley have too few HP because 'coding is complicated'. If an intern can't add a 0 to the HPs of the bosses in Alterac Valley in one day there's something really wrong with the way Blizzard codes things. Now, it is hard to know whether adding a 0 to their HP is sufficient, or even the correct thing to do. This is because DESIGN is hard, but coding is not hard. In fact, most coding stuff is trivial especially in light of game balance. Even when talking about additional content, mostly you don't get them because the company either wants more money for it or they're not sure if it's worth the investment. If your favorite MMORPG lets you have complete control to all their source code, you can probably implement almost any numerical change you'd want in under a week. There's no guraanteed if the resulting game would even be playable but you can definitely do it. I mean I know sometimes somethings that appear to be simple turns out to be surprisingly hard, but adding a 0 to the HP value of some enemy is not one of these things.
Well, assuming you already know what the change is going to be, it's cleared with producers, implementing a change in HP should be as simple as changing the value in an XML. Then the remaining time is testing and deploying.
I would agree that Blizzard is lying on this one.